Refrigerant evaporator



Aug, fr 1948.

P. HAYMOND REFRIGERANT EVAPORATOR Filed Jan. 18, 1945 PAUL INVENTOR.

HYMUNB io, is

Patented if S PATENT The present invention relates to an evaporator fora refrigerating system and more particularly to the type of evaporatorin which the sections forming the evaporator are connected so that theliquid refrigerant flows serially through said sections and alsoconnected so that gaseous or vapor refrigerant ows in parallel throughsaid sections.

One of the objects ci the present invention is to provide an evaporatorfor a refrigerating system having a plurality of substantiallyhorizontally disposed duct sections and in which a dem is disposedintermediate the duct sections, the dam stopping short of the top of theduct so as to dam the how of liquid. The adjacent section of the ductreceives liquid refrigerant which spills over the dam. In addition tothe outlet for gaseous refrigerant at the end of the last section toreceive refrigerant, there is provided another outlet or other outletsfor gaseous refrigerant intermediate the ends of the entire duct system.

In carrying out the foregoing object, it is a further object of thepresent invention to interpose the second mentioned gaseous refrigerantoutlet near the dam.

Furthermore, in carrying out the above mentioned objects, it is anobject of the present invention to arrangethe horizontally disposedsections of the duct in diierent planes and connect the same withvertically extending sections and to provide the inlet for liquidrefrigerant at the top of the evaporator and the last gaseousrefrigerant outlet at the bottom of the evaporator.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred form of embodiment of the invention isclearly shown.

In the drawings:

Fig. l is a diagrammatic view of a refrigerating system showing one formof my improved evaporator connected therein;

Fig. 2 is a, perspective view of one form of the improved evaporatorshowing only a fragment of the heat conducting ns;

Fig. 3 is a fragmentary sectional view of a portion of one of the ductsand showing the dam therein; and

Fig. i is a fragmentary sectional view taken on line 3 6 of Fig. 3.

The present evaporator is suitable for substantially any type ofartiiicial refrigerating system and for the purpose of illustrating oneform of the invention, I have shown the same as applied to a'refrigerating system of the compressor-condenser-expansion type.Referring to the drawings, `a compressor 20 is shown as driven by anelectric motor 2l through pulleys 22 and 23 and a Ibelt 2i. Thecompressed refrigerant from the compressor enters a condenser Zitwherein the gaseous refrigerant is liqufled and ls conducted from thebottom of the condenser 26 by a pipe 2l to a pressure reducing element28, whence the refrigerant under low pressure Iiows to the evaporator,which is generally indicated by the numeral 30. Gaseous refrigerant iswithdrawn from the evaporator 30 through a pipe 3i to the low pressureside of the compressor 20.

The evaporator 30 is shown enclosed in a refrigerator box 32 forming arefrigerated compartment 33. The operation of the motor is controlled byeither the temperature of the evaporator or the compartment cooledthereby and is herein shown as being controlled by the temperature ofthe compartment 33. For this purpose, there is provided a snap actingswitch 34 for interrupting and completing the circuit through theIelectrical conductor 35, The other electrical conductor is shown at 3B.The snap acting switch is actuated through a bellows 38 which isconnected by a small diameter tube 39 which terminates in thecompartment 33. The bellows 38 and tube 39 contain an expansible andcontractible fluid.

Any suitable type of lpressure reducing element may be employed betweenthe condenser 26 and the evaporator 30 and the element hereindiagrammatically shown at 28 is shown as a thermostatically controlledexpansion valve. This type of valve usually employs a needle valve whichis actuated'by a diaphragm and the diaphragm is subjected to thepressure in the evaporator for increasing the flow of refrigerant to theevaporator upon decrease in pressure of refrigerant in the evaporatorand vice versa, and the action of the needle is modied in response tothe temperature at the outlet of the evaporator, the effect being toclose the needle valve upon its seat when the temperature of the outletof the evaporator decreases to a predetermined temperature. For thispurpose, there is provided a closed thermostatic system including atemperature responsive element 4| which is suitably clamped at theoutlet of the evaporator and which is connected by a tube 42 to thevalve 28. This thermostatic system also includes an expansible andcontractible fluid.

Referring -speciiically to Fig. 2, the inlet to the evaporator 30 is at44 and the outlet at 45. The

duct means which forms the evaporator com' 3 prises a plurality ofelongated and substantially horizontally disposed duct sections 48 and41 which are connected with like-sections disposed in differenthorizontal planes by vertically extending duct sections 48 and 49.Suitable heat conducting fins 5| are attached to the ducts.

A plurality of dams 52 are provided at suitably spaced intervals, Thesedams 52 stop short of the top of the duct so as to provide an over-flow`the next dam 52 and so on until all tubes on the w same'horizontal planeare filled. When the last section on the horizontal plane is filled theliquid will overflow the last dam 52 down the duct 48 to the firstsection of the next horizontal duct and continue overflowing dams onthis horizontal group of tubes until it reaches vertical duct 49 and soon until it reaches the last dam 52, close to the outlet 45.

When the liquid overows the last dam at 45 the coil will be lled with apredetermined amount of liquid to the proper levels in each sectioncreated by dam 52. The liquid spilling over the last dam close to 45will have a cooling` affect on the duct connecting the evaporator to thecompressor. The bulb 4| controlling expansion valve 28 clamped to theduct 3| at a point close to 45 so that the affect from the liquidspilling over the last dam will stop the flow of refrigerant throughexpansion valve 28.

By providing the dams as herein disclosed, liquid refrigerant ismaintained throughout substantially the entire length of the evaporatorof the type in which all sections thereof are connected in seriescircuit relation. Gaseous refrigerant generated in one section can flowto the next adjacent 'section over the tops of the dams 52.

I have discovered that highly improved results are obtained bywithdrawing gaseous refrigerant at intervals throughout the length ofthe duct system and in the present embodiment, two supplementary gaseousoutlets are disclosed. These outlets are provided by ducts 53 and 54which are connected by a fitting 55 to a duct 56 which, in turn, isconnected to the main outlet end of the evaporator by a fitting 5l. Itwill, of course, be understood that the inlet end of the duets 53 and 54are connected to the top of the respective horizontal duct sections soas to provide for the free flow of gaseous refrigerant from theevaporator duct sections. By providing a plurality of supplementaryoutlets, as herein disclosed, a substantially equal pressure ismaintained throughout the length of the duct system of the evaporator.

One of theA advantages of the present invention is that a substantiallyeven temperature is maintained throughout the entire height of theevaporator. This advantage is attributed to the fact that liquidrefrigerant is substantially equally distributed throughout the entireevaporator, to the fact that substantially equal pressure is maintainedthroughout the length of the evaporator and to the fact that, at times,the refrigerant effect at the top of the evaporator 1S greaterl than thebottom to thus compensate for the decrement of air temperaturedescending about the fins and ducts of the evaporator. A refrigerantsystem of the type herein shown is usually operated cyclically i. e. ithas a running phase and an idle phase. At the start of the runningphase, the refrigerating effect at the top of the evaporator will begreater than at the bottom because the liquid refrigerant will ll theupper levels before it overflows to the next'lower level. The respectivesucceeeding next sections will not receive liquid refrigerant until itoverflows the dam in the predecessor sections. Thus, at times, thesurface of the next preceding section is'in contact with liquidrefrigerant longer with the result that at times the refrigeratingeffect is greatest at the top of the evaporator and progressivelysomewhat less, downwardly.

Under certain conditions, it may be desirable to maintain more liquidrefrigerant in the upper part of the evaporator than in the lower part,or vice versa, and in such case, the levels of liquid refrigerant can bevaried by providing dams of different heights. However, in generalpractice, it has been found that substantially the same temperature canbe maintained throughout the entire height of the evaporator with damsof equal height.

Often it is necessary to operate the evaporator at such a temperaturethat frost collects thereon. By virtue of the present invention, thethickness of frost upon the ns is substantially the same throughout theheight of the evaporator although the top of the evaporator is subjectedto the warmest downwardly circulating air. This is attributed to thefact that the mean refrigerating effect is greatest at the top of theevaporator and the lowest at the bottom due to the pro- .gressivespilling of liquid refrigerant from the top toward the bottom of theevaporator after the starting of the running phase. Several long soughtadvantages follow from this construction. During 'the major part of therunning phase, liquid refrigerant is substantially equally distributedthrough the entire length of the evaporator and this naturally enhancesthe efflciency of the refrigerating system. Although ice may form'on thefins, the thickness thereof is substantially equal throughout the heightof the evaporator; the undesirable insulating characteristics of theice, which tends to impair the efficiency of heat exchange between theair and the liquid refrigerant is minimized by causing the same tospread substantially equally throughout the height of the evaporator. Inthis manner, the differential between the temperature of the liquidrefrigerant and the desirable air temperature can'be reduced, thusresulting in a higher liquid refrigerant 'temperature and an improvementof the efficiency of the system. Moreover, it is necessary, atintervals, to defrost the ice `from the evaporator. Since the ice isdistributed substantially evenly on the fins and ducts throughout theheight of the evaporator, complete defrosting will occur substantiallysimultaneously throughout the entire height'of the evaporator and inthis manner, the defrosting period can be minimized.

While the form of embodiment of the present invention as hereindisclosed constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of claimswhich follow:

I claim:

1. An evaporator for a refrigeratingsystem comprising duct means formingtwo elongated and substantially horizontally disposed duct sectionsarranged in different substantially horizontal planes and connected inseries circuit relation by a vertically extending duct section, one endof the upper section having means for connecting same with the highpressure side of a refrigerating system and the end of the lower sectionhaving means for connecting the same with the low pressure side of thesystem, means forming a dam in each of said sections, said dam meansstopping short of the top of the respective duct section in which it isdisposed for retaining a quantity of liquid refrigerant in each of thesections and providing for the free flow of gaseous refrigerant, andmeans for forming a second outlet for gaseous refrigerant, and adaptedto be connected with the low pressure side of said system, said secondoutlet being disposed intermediate the ends of the duct means.

2. An evaporator for a refr-igerating system comprising duct meansforming two elongated and substan'tially horizontally disposed ductsections arranged in different substantially horizontal planes andconnected in series circuit relation by a vertically extending ductsection, one end of the upper section having means for connecting samewith the high pressure side of a refrigerating system and the end of thelower section having means for connecting the same with the low pressureside of the system, means forming a dam in each of said sections, saiddam means stopping short of the top of the respective duct section inwhich it is disposed for retaining a quantity of liquid refrigerant ineach of the sections and providing for the free ilow of gaseousrefrigerant, and means forming a. second outlet connected with the ductmeans above the upper level of the darn forming means and intermediatethe ends of the duct means, said second outlet being adapted to beconnected with the low pressure side of said system.

3. An evaporator for a refrigerating system comprising duct meansforming two elongated and substantially horizontally disposed ductsections arranged in different subst-antially horizontal planes andconnected in series circuit relation by a vertically extending ductsection, one end of the upper section having means for connecting samewith the high pressure side of a refrigerating system and the end of thelower section having means for connecting the same with the low pressureside of the system, means forming a dam in each of said sections, saiddam means stopping short of the top of the respective duct section inwhich it is disposed for retaining a quantity of liquid refrigerant ineach of the sections and providing for the free ilow of gaseous Arefrigerant, and means forming a second outlet for gaseous refrigerantconnected with the duct means adjacent said dam forming means andadapted to 'be connected with the low pressure side of the system.

4. An evaporator for a refrigerating system comprising duct meansforming two elongated and substantially horizontally disposed ductsections arranged in different substantially horizontal planes andconnected in series circuit relation by a vertically extending ductsection, one end of the upper section having means for connecting samewith the high pressure side of a refrigerating system and the end of thelower section having means for connecting the same with the low pressureside of the system, means forming a dam in each of said sections, saiddam means stopping short of the top of the respective duct section inwhich it is disposed for retaining a quantity of liquid refrigerant ineach of the sections and providing for the free ow of gaseousrefrigerant, and means forming a second outlet connected with the ductmeans adjacent said dam and above the upper level of the dam formingmeans, said second outlet being adapted to be connected with the lowpressure side of the system.

PAUL HAYMOND.

REFERENCES CITED The following references are of record in the file ofthis patent: 1

UNITED STATES PATENTS

